The chassis of an electronic apparatus, such as a laptop personal computer (laptop PC) or a convertible tablet type personal computer (convertible PC), are rapidly becoming thinner. A laptop PC has a configuration in which, for example, a display chassis is connected to a main unit chassis such that the display chassis can be opened and closed with respect to the main unit chassis from about a zero-degree position to about a 180-degree position through a hinge mechanism. A convertible PC has a configuration in which a display chassis is connected to a main unit chassis such that the display chassis can be flipped from a zero-degree position to a 360-degree position with respect to the main unit chassis through a hinge mechanism.
Normally, the chassis of this type of electronic apparatus includes a keyboard assembly, which is provided with a plurality of keytops elastically supported so as to be vertically movable, and various function switches. The keyboard assembly, for example, is required to provide satisfactory keystrokes to secure great ease of operation, resulting in an increased thickness of the chassis. In addition, the keytops of the keyboard assembly usually project from a surface of the chassis, so that the keyboard assembly may interfere with the display assembly when the display chassis is closed. It has been necessary, therefore, to further increase the thickness of the chassis in order to avoid the interference.
Hence, the present applicant has proposed, in Patent Document 1, a configuration in which the keytops can be pushed down to be accommodated as a display chassis pivots. In this configuration, a key depressing mechanism which moves the keytops up or down in synchronization with the rotation of a hinge mechanism is provided, so that the keytops move down when the display chassis is closed and the keytops move up when the display chassis is opened. This arrangement enables the keyboard assembly to be substantially thinner and also ease of operation to be secured.
[Patent Document 1] Japanese Patent No. 5980374
Normally, keytops are urged upward by elastic members, such as rubber domes. In other words, according to the configuration described in Patent Document 1 mentioned above, the keytops must be moved down against the urging force of the rubber domes when depressing the keytops. On the other hand, when moving the keytops upward, the urging force of the rubber domes will be an assist force.
Thus, in the foregoing key depressing mechanism, there is a significant difference between the load applied when the keytops descend and the load applied when the keytops ascend. This means that the key depressing mechanism and the hinge mechanism interlocked with the key depressing mechanism are subjected to high load at the descent, leading to a danger of damage or malfunction. A solution to this problem would require increasing the size and the strength of the components constituting the key depressing mechanism and the hinge mechanism interlocked with the key pressing mechanism. This, however, would impede achieving a thinner design. In addition, various function switches and the like other than the keyboard assembly may have the same problem.